The classification of pseudomonads and other obligately aerobic gram-negative bacteria from british pork sausage and ingredients.

On the basis of a computer analysis of 126 characters for each of 20 stock cultures and 165 isolates of Gram-negative, aerobic bacteria from fresh and processed pork, 138 isolates were identified with Pseudomonas. These were separated into 5 major clusters and 1 minor group. Twelve isolates were identified with Moraxella, 4 with Alteromonas and 11 were left unassigned. The identification of 101 isolates with Pseudomonas fragi provides substantive evidence that this species is the principal aerobic, Gram-negative contaminant of freshly butchered, stored or processed pork. Fluorescent pseudomonads were minor contaminants; 13 of our isolates were identified with Pseudomonas fluorescens biotype A, 8 with biotype C and 16 tentatively with biotype G. A simple determinative key for the routine identification of these organisms is given.

Attributes of microbial associations of meat growing as xenic batch cultures in a meat juice at 4 degrees C.

Strains of Gram-positive (Carnobacterium piscicola, Leuconostoc mesenteroides subsp. mesenteroides, Brochothrix thermosphacta) and Gram-negative (Pseudomonas fragi and Hafnia alvei) bacteria isolated from minced lamb packaged under a modified atmosphere were cultivated in a meat (lamb) juice at 4 degrees C. Carbohydrates were catabolised in the order glucose > glucose 6-phosphate during the development of the population. Under an atmosphere enriched with carbon dioxide the Gram-negative portion of the population was suppressed during the exponential phase but H. alvei became the dominant organism towards the end of a protracted stationary phase of growth. With the aerobic atmosphere P. fragi catabolised creatine and became the dominant species in the stationary phase. The inability of C. piscicola to catabolise glucose 6-phosphate was reflected in its population being smaller than those of the other Gram-positive organisms (C. piscicola < L. mesenteroides subsp. mesenteroides < B. thermosphacta). During the stationary phase of growth, indigenous L-lactic acid and the D-isomer produced by leuconostocs were oxidised to acetic acid by the Gram-positive flora under an atmosphere enriched with carbon dioxide. These oxidations, which occurred after depletion of glucose, were supported by the oxygen in the system. D-Lactic and acetic acid appeared to be possible parameters for the estimation of the microbiological quality of packaged meat.

The microstructure of the cuticle-less shell of the eggs of the domestic hen.

Open pores were a notable feature of the shell of hens' eggs which were naturally devoid of cuticle. In contrast with normal eggs, the surface of the cuticle-less shell was irregularly contoured and, in many instances, deeply fissured.

Growth of Salmonella enteritidis in artificially contaminated hens' shell eggs.

The effect of some factors on the growth of Salmonella enteritidis phage type 4 in artificially contaminated shell eggs was investigated. Salmonella enteritidis was found to be resistant to the antimicrobial properties of the albumen. Growth occurred on storage at 25 degrees C but not at 4 or 10 degrees C. The rate and extent of infection was influenced by the size of inoculum, the site of contamination relative to yolk movement, and the presence of iron in the inoculum.

Metabolic activities of pseudomonads in batch cultures in extract of minced lamb.

Pseudomonas fragi, Ps. lundensis and Ps. fluorescens were studied in axenic batch cultures growing in a lamb juice (pH 6.0) aerobically or in an atmosphere (Ps. fragi only) enriched with carbon dioxide at 4 degrees C. With all but a glucose dehydrogenase-deficient strain of Ps. fluorescens there was a sequential catabolism of glucose and lactate. Diauxic growth was observed in a nutrient-deficient meat juice supplemented with glucose and lactate. A transient peak in the concentration of gluconate and pyruvate was associated with the catabolism of glucose and lactate respectively. With Ps. fluorescens deficient in glucose dehydrogenase there was simultaneous catabolism of glucose and lactate. The stereoisomers of lactate were catabolized simultaneously in a laboratory medium. Glucose-6-phosphate was oxidized to 6-phosphogluconate by Ps. fragi and Ps. lundensis under aerobic conditions only. Creatine and creatinine were catabolized by Ps. fragi under aerobic conditions only. There was a slight decrease in the concentration of total amino acids (ninhydrin-reactive material) during the exponential phase of growth. The results suggest that the dominance of Ps. fragi in the climax populations in meat is due to catabolism of amino acid related substrates, creatine and creatinine.

The influence of sodium chloride and pH on the growth of Salmonella enteritidis PT4.

Sodium or potassium chlorides at concentrations of ca 2.0% (w/v) stimulated the growth of Salmonella enteritidis PT4 and PT6 but not PT8 in nutrient broth acidified to < or = 5.5 with acetic but not with citric, propionic or hydrochloric acids. Stimulation was noted also with an acidified defined medium. The most pronounced stimulation occurred with incubation at 37 degrees C. Supplementation of acidified nutrient broth with sucrose or glycerol had no effect on the growth of salmonellas.

The influence of incubation temperature and pH on the antimicrobial properties of hen egg albumen.

Gram positive bacteria, including lysozyme-resistant strains, and yeasts were killed in hen egg albumen with or without iron at 30 of 39.5 degrees C. The albumen was more toxic at 39.5 degrees C than at 30 degrees C for Gram negative bacteria. With the exceptions of Pseudomonas fluorescens, Acinetobacter sp. and Proteus vulgaris, iron caused the growth of Gram negative bacteria or protected them from being killed in hen albumen at 39.5 degrees C. At this temperature, however, maximal growth of and glucose utilization by Escherichia coli C20 only occurred in albumen supplemented with growth factors, trace metals, additional nitrogen and sufficient iron to quench ovotransferrin. The bactericidal properties of albumen could be negated by changing its pH from 9.0 or above to 7.5 or below. At 39.5 degrees C, enterochelin allowed growth of E. coli in albumen at pH 7.9, but not at 9.4, whereas iron allowed growth at both pH values.

The incidence and level of contamination of British fresh sausages and ingredients with salmonellas.

A five-tube most probable number (MPN) method, with the pre-enrichment and enrichment stages, was used in a study of the incidence of salmonella contamination of British fresh sausages and the ingredients used in their manufacture. All samples were taken from a large factory in the course of routine production. There was an incidence of 65% contamination of pork (n = 20) and 55% (n = 20) in pork and beef sausages. The incidences of contamination of uncooked ingredients varied from 95% for mechanically recovered meat (n = 20) to 10% for another type of meat. Cooked and/or dried ingredients were rarely contaminated with these organisms, and when contamination occurred, coliforms were also important. The numbers of salmonellas isolated ranged from 7-40 for pork sausages, from 8-24 for beef and pork sausages and from 0.8-378 organisms/g for ingredients. The following salmonella serotypes were isolated (ranked in descending order or incidence): S. derby, S. dublin, S. newport, S. stanley. S. typhimurium, S. heidelberg, S. infantis and S. agona.

Vaterite, a constituent of the eggshells of the nonparasitic cuckoos, Guira guira and Crotophagi ani.

The crystalline spherules occurring in patches on the outer surface of the eggshells of Guira guira and the bloom on the entire outer surface of those of Crotophagi ani were shown by X-ray diffraction analysis to be vaterite.

A study of sulfite-tolerant yeasts from comminuted lamb products.

The sulfite tolerance of meat yeasts was shown to be determined by pH, sulfite concentration, substrate availability, and the composition of the preincubation medium. Acetaldehyde production by Candida norvegica was sulfite-induced and occurred during the exponential growth phase in sulfited (500 micrograms SO2 ml-1) lab lemco glucose broth cultures buffered at pH 5, 6, or 7. Growth at pH 4, however, was inhibited by sulfite. Acetaldehyde production occurred in sulfited medium containing fructose or ethanol but not lactate nor a range of other assimilable substrates. A non-acetaldehyde-producing yeast, Candida vini, grew in sulfited (500 micrograms SO2 ml-1) lab lemco broth containing glucose or lactate buffered at pH 6 or 7 but not at pH 4 or 5.

The influence of temperature on the behaviour of mixed bacterial contamination of the shell membrane of the hen's egg.

The inner membrane of the air cell of hens' eggs was inoculated with Pseudomonas putida, Staphylococcus xylosus, Enterococcus faecalis, Escherichia coli and Salmonella enteritidis. The first mentioned eventually dominated the contamination of the albumen of eggs stored at 4, 15, and 20 degrees C. The last mentioned did so in eggs stored at 37 degrees C. The interval between inoculation of the membrane and gross contamination of the albumen was markedly influenced by site of contamination relative to yolk movement.

Persistence of contamination of hens' egg albumen in vitro with Salmonella serotypes.

A study was made of the persistence of different Salmonella serotypes in hens' egg albumin in vitro at 4, 20 and 30 degrees C. The majority of serotypes remained viable but did not increase in numbers at 20 and 30 degrees C for 42 days. At 4 degrees C many of the serotypes died out. The addition of ferric ammonium citrate on the 42nd day of incubation induced multiplication of organisms incubated at 20 and 30 degrees C, but not at 4 degrees C. The pH and glucose concentration of the albumen diminished only when heavy growth occurred. Salmonella enteritidis remained viable on the air cell membrane in vitro for 17 days at 4, 20 and 30 degrees C. Thirty percent of the organisms also remained motile in albumen for 42 days at 25 degrees C and up to 5% of the cells remained motile for up to 20 days at 4 degrees C.

Effect of faecal extract on the growth of Salmonella enteritidis in artificially contaminated hens' eggs.

1. Salmonella enteritidis PT 4 grew in eggs stored at 25 degrees C, but not at 10 degrees C. 2. The incidence of generalised infection of the egg contents (greater than 10(6) salmonellas/ml) was greater in eggs inoculated with cells suspended in faecal extract compared to those with cells in Ringer's solution. 3. The removal of most of the iron did not decrease the growth-promoting effect of the faecal extract.

Effect of phenolic compounds and oleuropein on the germination of Bacillus cereus T spores.

The phenolic compounds extracted from olives with ethyl acetate inhibited germination and outgrowth of Bacillus cereus T spores. Purified oleuropein, a well-characterized component of olive extract, inhibited these processes also. The addition of oleuropein and olive extracts 3 or 5 min after germination began, immediately decreased the rate of change of phase bright to phase dark spores and delayed significantly outgrowth.

A pulse-position-modulated multichannel radio telemetry system for the study of the avian nest microclimate.

A multichannel biotelemetry system using pulse position modulation has been developed to monitor continuously the environment in birds' nests. Probes to measure temperature at six points, relative humidity, light and egg attitude, together with a transmitter and power supply are contained in a fibreglass shell, having the shape, size and weight of the egg of the species being studied. The sensing egg is placed in the nest at the completion of a clutch and not removed until the young have hatched. A low-power transponder is used to relay the signals up to 2 miles to a data-logging system in the laboratoy.

Crystal orientation in the shell of the domestic fowl: an electron diffraction study.

The eggshell of the domestic fowl has been studied by transmission electron microscopy and diffraction. Thin sections of shell were prepared by chemical and ion-beam thinning techniques. Each calcite column of the palisade layer consisted of crystallites of diameter 20 to 30 micrometer with some tendency for crystallite alignment within a single column. Evidence indicates that there was no significant preferred orientation in the palisade layer as a whole. Only in the surface layer was any preferred orientation detected, and here (1014) planes tended to lie parallel to the surface. The results are compared with previously published data, and calcite nucleation and growth are discussed.